1922. Xo. 5- ARIOXIDAE OF NORWAY. II 



(1916I, according to whom several species feed on earth, and obtain the 

 necessar}- quantity of water by lapping it up. Thus Arioii atcr and Avion 

 sttbfusciis are capable of consuming up to about i ' 2 times their own weight 

 of water in less than twenty four hours. 



In the treatise above mentioned Kunkel describes very detailed studies 

 on the reproduction of Arions, and in the present section there will only 

 be summarized the results of some of his admirable investigations. 



In the ovotestis are first formed sperms, later on even ovo. The 

 former are enclosed in the spermatophore, which is fashioned in the epi- 

 phallus immediately before congress. Then takes place a mutual and simul- 

 taneous exchange of spermatophores (in Arion intcruicdiiis the latter have 

 not vet been found; I have discovered it in Arion ci)XuniscriptHs\. Curiously 

 enough, the sperms lose their spiral tail in the receptaculum, and the said 

 author infers that this is necessary to fulfil impregnation. Animals even 

 multiply that are kept isolated long before maturity, and the author con- 

 cludes that this is due to a self-fertilisation. 



Six to eight weeks after maturity, the deposition of eggs begins, and 

 takes place in several hatches, each having a period of from 12 to 26 hours, 

 during which the animal does not stir. The tentacles are withdrawn, and 

 the slug is not disturbed even if taken into the hand. 



In one and the same species the eggs vary in size and number, and 

 thev are often unlike even in the same hatch; Arion circuniscriptiis and 

 Arion horlcnsis have oval eggs, Arion atcr, Ario)i siibfiisciis and Arion 

 intermedins both oval and globular eggs. The shell-membrane contains 

 calcareous particles, either in the form of crystals (Arion circianscriptiis, 

 Arion /lortcnsis, Arion intcrnicdiiis) or rounded granulations [Arion atcr and 

 Arion snb/nsciis). 



The embrvology cannot be discussed in this paper. As to the duration 

 of life I need only state that none of the Arions exceed an age of 

 1 4 mouths. 



Key to the Norwegian Arions, as regards external 



characters.^ 



I. Large (more than 7 cms. when extended), usually black or white. 

 Mucus as a rule colourless and tenacious. S/iie/d-bands absent {sometimes 

 appear in the young, ninning anteriorly close to each other, approximately 

 as straight lines). Arion atcr. 



' In using the key attention should be paid to the following facts : The colour of these 

 animals varies in all species, often to a perplexing degree, and is generally altered 

 by alcohol so as to complicate the determination ; thus it is impossible to decide 

 whether the foot-sole was white or yellow in the living animal. However, I have found 

 the shield-bands to afl'ord excellent characters in the majorit\- of cases (sometimes 



